Acetabular reamer

ABSTRACT

An acetabular reaming system is disclosed of the type having a driver and a tool held together by a quick-release coupling mechanism. The tool ( 10 ) has a hollow body ( 12 ) defining a domed shape with a rotational axis ( 14 ), an apex ( 16 ) aligned with the axis ( 14 ) and a hemispherical wall ( 18 ) extending from the apex ( 16 ) to an equatorial rim ( 20 ) spaced 90 degrees from the axis ( 14 ). The rim ( 20 ) has an edge ( 22 ) visible to the user that indicates the position of the tool ( 10 ) relative to the bone. A first plurality of cutting sites ( 24 ) is arrayed along the body ( 12 ) and a second plurality of cutting sites ( 28 ) is arrayed circumferentially along the edge ( 22 ). Preferably, the first plurality of cutting sites ( 24 ) present raised first teeth ( 30, 130, 230, 330 ) having a profile selected from continuous squared ( 30 ), continuous rounded ( 130 ), discontinuous squared ( 230 ) and tongued ( 330 ) profiles. Also preferably, the second plurality of cutting sites ( 28 ) present raised second teeth ( 32, 132, 232, 332, 432 ) selected from continuous squared ( 32 ), continuous rounded ( 132 ), discontinuous squared ( 232 ), tongued ( 332 ) and bladed ( 432 ) profiles.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/084,191, filed on Apr. 11, 2011, now U.S. Pat. No. 8,784,422, whichis a divisional of U.S. patent application Ser. No. 10/266,442, filed onOct. 8, 2002, now U.S. Pat. No. 7,922,721, which claims priority fromU.S. provisional application Ser. No. 60/328,154, filed on Oct. 9, 2001.

TECHNICAL FIELD

The present invention relates to surgical cutting tools andinstrumentation systems that utilize such tools, particularly toolshaving a domed shape for reaming a hemispherical bone cavity.

BACKGROUND

Acetabular reaming systems are well known in hip arthroplasty, toprepare bone tissue for receiving a hemispherical implant U.S. Pat. No.5,658,290 to one of the present inventors, the entire contents of whichare expressly incorporated by reference herein and relied-upon,discloses such a system. In the afore-mentioned patent, a surgicaldriver includes a quick disconnect mechanism having catches that receivea pair of orthogonal bars from a domed cutting tool.

It is highly desirable that the bone is shaped by the rotary tool into acavity that conforms closely in hemispherical shape and dimension to theimplant being received. Those skilled in the art have sought to providerotary cutting tools that form the bone into a precise hemisphericalcavity. It is further desirable to advance the tool linearly into thebone to fully cut the cavity, versus having to rock the tool sideways bychanging its orientation to achieve a complete shape.

For example, one system has a tool with a cylindrical rim that continuesparallel past the hemispherical equator of the tool, in order to allowpresentation of teeth for a full cut. Such prior domed tools arereferred to as “high-rim” reamers. Although these high-rim reamers haveteeth presented for a straight-in (linear) advancement of cut into thecavity, there is no visual confirmation guiding the user to the finishedcut. Actual position of the outer equatorial edge of the tool in thebone cavity is obscured and the user does not know exactly when to stoppushing in the tool.

Another type of tool is found in what is known as “hemispherical”reaming systems. These tools have no teeth presented for a full cut ofthe cavity simply by linear advancement of the tool into the bone. Thatis, a full, a straight-in cut is not possible hence the tool must berocked sideways in order to present the teeth for cutting the finalshape. This may result in over-cutting of the cavity.

Accordingly, a need exists for an improved reaming system wherein theuser may precisely ascertain the swath being cut by the tool as itbottoms-out in the bone, to completely form the hemispherical-shapedcavity without the risk of over-cutting. Particularly, there is a needfor visual confirmation by the user of the position of the equatorialedge of the tool as the cavity is being fully cut.

There is also a need for an improved. reaming system wherein the tool islinearly advanced without having to “rock” the tool by changing theorientation of the cutting approach, in order to achieve a full cut.

There is a further need for a rotary cutting tool having a tooth designthat precisely cuts a cavity with the desired size and shape of animplant to be received in the cavity, while employing a linear cutguided by accurate visual confirmation by the user.

SUMMARY OF INVENTION AND ADVANTAGES

According to an embodiment of the present invention, there is provided atool for cutting a hemispherical cavity in bone. The tool is preferablypart of a reaming system. that utilizes a driver with quick disconnectcatches that receive mounting bars on the tool. The tool has a hollowbody defining a domed shape with a rotational axis, an apex aligned withthe axis and a hemispherical wall extending from the apex to anequatorial rim spaced 90 degrees from the axis. The rim has an edgevisible to the user that indicates the position of the tool relative tothe bone. A first plurality of cutting sites is arrayed along the bodyand at least one equatorial cutting site is located along the edge.Preferably the first cutting sites are open and the equatorial siteclosed.

In a preferred embodiment, the first plurality of cutting sites presentraised first teeth having a profile selected from squared, rounded andtongued profiles.

In another preferred embodiment, the equatorial cutting site of the toolpresents a raised second tooth selected from squared, rounded, tonguedand bladed profiles.

According to another embodiment of the invention, the tool has a hollowbody defining a domed shape with a rotational axis, an apex aligned withthe axis and a hemispherical wall extending from the apex to anequatorial rim spaced 90 degrees from the axis. The rim has an edgevisible to the user that indicates the position of the tool relative tothe bone. A first plurality of cutting sites is arrayed along the bodyand a second plurality of cutting sites is arrayed circumferentiallyalong the edge. Preferably, the first plurality of cutting sites presentraised first teeth having a profile selected from squared, rounded andtongued profiles. Also preferably, the second plurality of cutting sitespresent raised second teeth selected from squared, rounded, tongued andbladed profiles.

According to yet another embodiment of the invention, the tool has ahollow body defining a domed shape with a rotational axis, an apexaligned with the axis and a hemispherical wall extending from the apexto an equatorial rim spaced 90 degrees from the axis. The rim has anedge visible to the user that indicates the position of the toolrelative to the bone. A first plurality of cutting sites is arrayedalong the body and a second plurality of cutting sites is arrayedcircumferentially along the edge on downwardly depending lobes, whichlobes preferably continue with substantially the same radius ofcurvature past the equator of the tool. Preferably, the first pluralityof cutting sites present raised first teeth having a profile selectedfrom squared, rounded and tongued profiles. Also preferably, the secondplurality of cutting sites present raised second teeth selected fromsquared, rounded and tongued profiles.

In still another embodiment of the invention, the tool has a hollow bodydefining a domed shape with a rotational axis, an apex aligned with theaxis and a hemispherical wall extending from the apex to an equatorialrim spaced 90 degrees from the axis. The rim has an edge visible to theuser that indicates the position of the tool relative to the bone. Atleast one mounting bar, and preferably a pair of, mounting bars, extendsacross the underside of the body between diametrically opposed locationson the rim. A first plurality of cutting sites is arrayed along the bodyand a second plurality of cutting sites is outboard of the diametricallyopposed. locations at the edge. Preferably, the second plurality ofcutting sites is closed. It is also preferred that the second pluralityof cutting sites present bladed teeth essentially extending outboardfrom the bars.

Thus, in one embodiment the present invention relates to a tool forcutting a hemispherical cavity in bone, comprising: a hemispherical,hollow dome extending from an apex to an equatorial rim, wherein arotational axis central to the dome is aligned with the dome apex andwherein the equatorial rim is spaced from the rotational axis; at leastone mounting bar extending perpendicular to the rotational axis withspaced apart ends secured to opposed locations of the dome; a pluralityof first cutting teeth arrayed along the dome, but spaced form theequatorial rim thereof; at least two second cutting teeth, each secondcutting tooth located at the equatorial rim and characterized as being aportion of the material of the dome having been raised in an upwardlydirection to provide a second cutting edge of a cutting radii spacedfurther from the rotational axis than a hemispherical radii of thehemispherical dome to thereby interrupt the hemispherical continuity ofthe equatorial rim with the second cutting edge; and wherein the cuttingradii and the hemispherical radii are each measured from a point wherethe rotational axis and an equatorial plane of the dome alignedperpendicular to the rotational axis meet.

An advantage of the present invention is the capability to perform anessentially perfect hemispherical cut, where the depth can be assessedclearly during the cut.

Another advantage of the invention is a tool presenting cutting sitesthat allow a full cut with clear visual confirmation while the userlinearly advances the tool into the bone, without needing to change theorientation of the surgical driver and hence ‘rock’ the tool.

A further advantage of the invention is that, in preferred embodiments,the equatorial teeth are contained at closed cutting sites, which avoidsrisk of tissue entrapment.

Other objects and advantages will become apparent to a reader skilled inthe art, with reference to the following Figures and accompanyingDetailed Description wherein textual reference characters correspond tothose denoted on the Drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational view of a tool of the present invention,showing an equatorial tooth with a preferred flattened profile;

FIG. 1A is a schematic view of the tooth configuration shown in FIG. 1;

FIG. 2 is an elevational view of the tool of the of FIG. 1, showing anequatorial tooth with a preferred rounded profile;

FIG. 2A is a schematic view of the tooth configuration shown in FIG. 2;

FIG. 3 is a perspective view of FIG. 1, showing an equatorial tooth witha preferred tongued profile;

FIG. 3A is a schematic view of the tooth configuration shown in FIG. 3,

FIG. 4 is a perspective view of a preferred tool of the invention,showing a closed equatorial cutting site containing a flattened toothprofile;

FIG. 5 is a perspective view of a preferred tool of the invention,showing closed equatorial cutting sites containing bladed teethrepresenting outboard extensions of the mounting bars;

FIG. 6 is an elevational view of a cutting tool of the presentinvention, showing equatorial cutting sites located on downwardlydepending lobes, which contain rounded teeth;

FIG. 6A is a schematic view of a representative equatorial cutting siteon a preferred downwardly depending lobe at the edge of the rim. of thebody shown in FIG. 6;

FIG. 7 is a perspective view of FIG. 6;

FIG. 7A, is a schematic view of the equatorial tooth configuration shownin FIG. 7; and

FIG. 8 is a perspective view of the reaming system of the invention,showing a tool and driver connected together and ready for use.

DETAILED DESCRIPTION

According to the present invention, there is provided a reaming systemfor cutting a hemispherical cavity in bone. Referring to FIGS. 1-7, thesystem has a tool 10 that utilizes a driver 11, shown in FIG. 8 withquick disconnect mechanism that receives the tool 10 for use. Thestructure and operation of driver 11 and its connecting mechanism isamply described in the aforementioned U.S. Pat. No. 5,658,290, which isessentially the same as the driver-tool mechanism shown by FIG. 8. Ofcourse, other connecting mechanisms could be employed, such as a centralboss provided on the tool, as described in WO 99/47051 of one of thepresent inventors. As shown by WO 99/47051, a single mounting bar couldbe used with one pair diametrically opposed ends, versus the pair ofintersecting mounting bars shown in the '290 patent mentionedimmediately above.

Referring to FIGS. 1-3, the tool 10 has a hollow body 12 defining adomed shape with a rotational axis 14, an apex 16 aligned with the axis14 and a hemispherical wall 18 extending from the apex 16 to anequatorial rim 20 spaced 90 degrees from the axis 14. The rim 20 has anedge 22 visible to the user that indicates the position of the tool 10relative to the bone. A first plurality of cutting sites 24 is arrayedalong the body 12 and at least one equatorial cutting site 28 is locatedalong the edge 22.

Referring to FIGS. 1-7, the first plurality of cutting sites 24 presentraised first teeth 30, 130, 230 preferably having a profile selectedfrom squared 30 (FIGS. 4-5), rounded 130 (FIGS. 7-8) and tongued 232profiles. A suitable tongued profile tooth 232 is taught in U.S. Pat.No. 5,968,049, the entire disclosure of which is incorporated byreference herein and relied upon. The tongued tooth 232 may either beserrated, as shown in U.S. Pat. No. 5,968,049, or non-serrated.Similarly, where the equatorial tooth 232 has a tongued profile (FIG.3), it is as shown in U.S. Pat. No. 5,968,049.

In FIG. 1A, the tooth 32 is formed or results from bending the tooth 32outward, leaving a flattened tooth with no side relief and roundededges. In FIG. 2, the rounded tooth 132 is commonly known as a “cheesegrater” tooth, manufactured with a high ram that is then later removed(FIG. 2A) to reveal a hemisphere with a cheese grater tooth-style at theedge.

Referring to FIGS. 1-3 and 5-7, the equatorial cutting site 28 presentsa raised second tooth 32, 132, 232, 332 selected from squared 32 (FIG.1), rounded 132 (FIGS, 2, 6-7), tongued 232 (FIG. 3) and bladed 332(FIG. 5) profiles,

Referring to FIGS. 1-7, the tool 10 has a hollow body 12 defining adomed shape with a rotational axis 14, an apex 16 aligned with the axis14 and a hemispherical wall 18 extending from the apex 16 to anequatorial rim 20 spaced 90 degrees from the axis 14. The rim 20 has anedge 22 visible to the user that indicates the position of the tool 10relative to the bone. A first plurality of cutting sites 24 is arrayedalong the body 12 and a second plurality of cutting sites 28 is arrayedcircumferentially along the edge 22. Preferably, the first plurality ofcutting sites 24 present raised first teeth 30, 130, 230, 330 having aprofile selected from squared 30, rounded 130, squared 230 and tongued330 profiles. Also preferably, the second plurality of cutting sites 28present raised second teeth 32, 132, 232, 332 selected from squared 32,rounded 132, tongued 232 and bladed 332 profiles. In FIGS. 1-3, body 12is formed by starting with a hollow domed shape, with the wall 18extending beyond the 90-degree equator (shown in phantom) and then cut.The equatorial teeth 32, 132, 232 are formed and wall 18 is then cut atthe 90-degree equator so that the teeth are open on their lower side.

Referring to FIGS. 6-7, the tool 10 has a hollow body 12 defining adomed shape with a rotational axis 14, an apex 16 aligned with the axis14 and a hemispherical wall 18 extending from the apex 16 to anequatorial rim 20 spaced 90 degrees from the axis 14. The rim 70 has anedge that is similar to the edge 22 shown in the embodiments in FIGS. 4and 5. This edge is visible to the user to indicate the position of thetool 10 relative to the bone. A first plurality of cutting sites 24 isarrayed along the body 12 and a second plurality of cutting sites 28 isarrayed circumferentially along the edge 22 on downwardly dependinglobes 36. The wall 18 continues past the equator of the tool 10 with thesame radius of curvature as the rest of wall 18, rather than being madecylindrical at the equator. This continued curvature assures that thecorrect shape is being cut, even if the tool 10 is not advanced entirelyin a linear fashion into the bone cavity being cut. Preferably, thefirst plurality of cutting sites 24 present raised first teeth 30, 130,230, 330 having a profile selected from squared 30, rounded 130, squared230 and tongued 330 profiles. Also preferably, the second plurality ofcutting sites 28 present raised second teeth 32, 132 selected fromsquared 32 or rounded 132 profiles. The lobes 36 curve downwardly andinwardly, having the same curvature as the upper part of the wall 18rather than being cylindrical in shape.

Referring to FIGS. 4-5, the body 12 has at least one mounting bar 34extending between the axis 14 and rim 20, with a tooth 32, 332 which, inFIG. 5 is an essentially contiguous radial projection or blade formedfrom the bar 34 outboard of the rim 20 along edge 22. The firstplurality of cutting sites 24 preferably contains openings 25 forpassage of debris, whereas the second plurality of sites 28 may beeither open. (FIGS. 1-2 and 6-7) or closed (FIGS. 4-5).

Preferably, the second plurality of teeth 32, 132, 232 arediscontinuous, i.e., relieved on one side, with respect to the tool 10shown in FIGS. 1-3, Teeth 32, 132, 232 are made discontinuous by cuttingaway the material of the body 12, shown in phantom (FIGS, 1-3) once theteeth are formed. Machining of the teeth 32, 132, 232 in body 12 isdepicted in FIGS. 1A, 2A and 3A, respectively. By contrast, in FIGS. 6-7the teeth 132 are continuous.

While one or more preferred embodiments of the present invention havebeen described, it should be understood that various changes,adaptations and modifications might be made without departing from thespirit of the invention and the scope of the appended claims.

What is claimed is:
 1. A tool for cutting a hemispherical cavity inbone, the tool comprising: a) a hollow, hemispherical wall portion of adome extending along a rotational axis from an apex to an equatorial rimof the dome, wherein the rotational axis intersects the hemisphericalwall portion at the apex, and wherein the equatorial rim is spaced fromthe rotational axis and resides on an imaginary equatorial plane alignedperpendicular to the rotational axis, wherein the hemispherical wallportion has a first outer radii measured from a focal point residing atwhere the rotational axis intersects with the imaginary equatorialplane; b) at least one mounting bar extending perpendicular to therotational axis and comprising spaced apart mounting bar ends secured toopposed locations of the hemispherical wall portion at the equatorialrim; c) a plurality of first dome cutting teeth arrayed along thehemispherical wall portion; and d) at least two second cutting teethformed from respective ends of the at least one mounting bar outboard ofthe equatorial rim along an edge of the hemispherical wall portionthereby interrupting the hemispherical continuity of the equatorial rimwith the at least two second cutting teeth, e) wherein at least one ofthe first dome cutting teeth and at least one of the second cuttingteeth are characterized as being wall portions of the hemispherical wallportion having been raised in an upwardly direction, and wherein each ofthe raised wall portions provides a dome cutting tooth sharp edge of acutting radii spaced further from the focal point than the first outerradii of the hemispherical wall portion, and f) wherein the plurality ofthe first dome cutting teeth face respective openings extending throughthe hemispherical wall portion for passage of debris into an interior ofthe hemispherical wall portion.
 2. The tool of claim 1, wherein theplurality of the first dome cutting teeth have a profile selected fromthe group consisting of squared, rounded, tongued, and combinationsthereof.
 3. The tool of claim 1, wherein the sharp edge of at least oneof the second cutting teeth has an edge profile selected from the groupconsisting of squared, rounded, tongued, bladed, and combinationsthereof.
 4. The tool of claim 1, wherein the at least one mounting barcomprises two mounting bars that intersect each other to form a cross.5. The tool of claim 4, wherein ends of the two mounting bars aresecured to locations that are spaced 90° from each other on the interiorof the hemispherical wall portion.
 6. The tool of claim 4, wherein theat least two second cutting teeth comprise four second cutting teeth,each being a second cutting tooth formed from a respective end of one ofthe two bars outboard of the rim along the edge of the hemisphericalwall portion.
 7. A tool for cutting a hemispherical cavity in bone, thetool comprising: a) a hollow, hemispherical wall portion of a domeextending along a rotational axis from an apex to an equatorial rim ofthe dome, wherein the rotational axis intersects the hemispherical wallportion at the apex, and wherein the equatorial rim is spaced from therotational axis and resides on an imaginary equatorial plane alignedperpendicular to the rotational axis, wherein the hemispherical wallportion has a first outer radii measured from a focal point residing atwhere the rotational axis intersects with the imaginary equatorialplane; b) two mounting bars, each mounting bar extending perpendicularto the rotational axis and comprising spaced apart mounting bar endssecured to opposed locations of the hemispherical wall portion at theequatorial rim, wherein ends of the two mounting bars are secured tolocations that are spaced 90° from each other on an interior of thehollow hemispherical wall portion; c) a plurality of first dome cuttingteeth arrayed along the hemispherical wall portion; and d) four secondcutting teeth, each second cutting tooth formed from a respective end ofone of the two mounting bars outboard of the equatorial rim along anedge of the hemispherical wall portion thereby interrupting thehemispherical continuity of the equatorial rim with the four secondcutting teeth, e) wherein at least one of the first dome cutting teethand at least one of the second cutting teeth are characterized as beingwall portions of the hemispherical wall portion having been raised in anupwardly direction, and wherein each of the raised wall portionsprovides a dome cutting tooth sharp edge of a cutting radii spacedfurther from the focal point than the first outer radii of thehemispherical wall portion, and f) wherein the plurality of the firstdome cutting teeth face respective openings extending through thehemispherical wall portion for passage of debris into the interior ofthe hemispherical wall portion.
 8. The tool of claim 7, wherein theplurality of the first dome cutting teeth have a profile selected fromthe group consisting of squared, rounded, tongued, and combinationsthereof.
 9. The tool of claim 7, wherein the sharp edge of at least oneof the second cutting teeth has an edge profile selected from the groupconsisting of squared, rounded, tongued, bladed, and combinationsthereof.